The invention concerns an internal gear pump having an internal gear; a pinion meshing with the internal gear and mounted eccentrically with regard to the internal gear; a shaft supporting the pinion; a central ring-shaped housing part encompassing the internal gear and pinion and containing a suction socket as well as a pressure socket; a ring-shaped housing intermediate part on each side of the central housing part, each in which the shaft is supported; and a cutout portion in each intermediate part, which extends bow-shaped in peripheral direction. A pump of this general type is known from DE 41 04 397 A1.
Internal gear pumps of this type are used in simplex design, i.e., as single pumps. Provided axially outside the ring-shaped housing intermediate parts, in such case, is a housing cover plate which endwise seals the interior of the housing. However, also two or several internal gear pumps can be combined by flanging them together equiaxially. The said cover plates are dispensable in such case between two adjacent pumps. Further, there are pumps where a so-called filler part with a pertaining filler part pin is arranged between pinion and ring gear, is essentially sickle-shaped and extends essentially across the last quadrant of the cavity between ring gear and pinion.
Of importance with such pumps is the output performance, and in particular, parameters such as pump volume, achievable pressures and efficiency. Of increasing importance is the noise performance. Ever greater significance is attached to it in the context of humanizing the workplace. Considerable success has been achieved in recent years in this regard. While the noise level with a specific, known design ranged in 1987 still at 78 JB(A), it measured 69 JB(A) in 1991. To accomplish this, the major design features were optimized. These concerned especially the internal gearing, plain bearings as well as the radial and axial compensation. However, a further reduction of the noise level has not been achievable with conventional measures, despite significant efforts. In certain cases it is even necessary to forego the utilization of high pressures, or expensive sound insulation measures must be taken.
The problem underlying the invention is to fashion an internal gear pump in such a way that the noise performance displays a distinct reduction beyond the results that have been achieved to date.